1. Field of the Invention
The present invention relates to an improvement in an assembly method of a preload-type, double-row ball bearing which has negative gaps respectively between an outer race and a plurality of balls and between the plurality of balls and an inner race after the double-row ball bearing is assembled and, in particular, to an assembly method of a preload-type, double-row ball bearing in which a plurality of balls in each row are distributed at equal intervals in a manner in which no flaws and indentations are formed in the race surfaces of outer and inner races and in the surfaces of the balls.
2. Description of the Art
U.S. Pat. No. 2,931,095 discloses a method of distributing balls by using an arrow-shaped jig, and a method of assembling a retainer. However, when these methods are applied to a preload-type ball bearing there is a fear of causing flaws by dragging in the raceway surfaces of the outer and inner races and in the surfaces of the balls due to a preload applied between the outer race and the balls and between the balls and the inner race during an operation of distributing the balls at equal intervals. Thus, there is a problem in which sounds and vibrations are generated by the flaws and satisfactory quality of the products cannot be insured.
U.S. Pat. No. 3,532,401 discloses an assembly method of a preload-type, double-row ball bearing. However, there is no description in this patented method as to the distribution of the balls at equal intervals after assembly of the ball bearing. Accordingly, the problem in the above-mentioned U.S. Pat. No. 2,931,095 is not solved.
Japanese Patent Laid-Open Publication No. 57-97914 discloses distribution of balls at equal intervals by reducing a preload by a loading thrust between the outer and inner races. However, since a minute ball indentation is apt to be caused in a raceway surface and in the ball surfaces due to the thrust, the problem of sound and vibrations in the above-mentioned U.S. Pat. Nos. 2,931,095 and 3,532,401 are not solved. Furthermore, another problem is caused in that control of the thrust is difficult.
Japanese Utility Model Publication No. 39-3916 discloses a technique for an angular ball bearing in which an assembly of an inner race, balls and a retainer is assembled from one side of another race which has been heated and expanded. However, the bearing disclosed herein is a single-row ball bearing and it is difficult for this technique to be applied to a preload-type, double-row ball bearing because the distance of insertion movement is long and control of the insertion is difficult. Therefore, there is a problem in which flaws by fitting and indentations are formed in the raceway surfaces and the ball surfaces. A further problem of generating sounds and vibrations is also involved as is the case in the above-mentioned U.S. Pat. No. 2,931,095.
Japanese Patent Laid-Open Publication No. 58-34724 discloses the disposition of the balls under a condition in which an inner race is deviated with respect to an outer race. Specifically, the outer race and the inner race are placed on a receiving table with the inner race deviated with respect to the outer race inside the outer race to thereby form a crescent-shaped gap between the outer and inner races. A predetermined number of balls are inserted in the crescent shaped gap and the outer and inner races are disposed substantially concentrically with respect to each other. Then the balls are fitted into the raceway grooves of the outer and inner races. However, the bearing which is assembled in this manner is not described as being a preload-type bearing and, thus, there is not disclosure as to concrete means for distributing balls at the time of assembly of the preload-type, double-row ball bearing. For this reason, in this prior art patent publication, the problem of the creation of flaws by dragging at the time of distribution the balls in the preload-type, double-row ball bearing is not solved. Thus, there is a problem similar to that in each of the prior art publications.
U.S. Pat. No. 3,340,590 discloses a method of distributing balls at equal intervals by using an arrow-shaped jig. However, the object bearing is not a preload-type bearing and, still further, the bearing is not a double-row type bearing. Accordingly, the problem in each of the prior art patent publications remains unsolved.